TRUE CRIME: Major Terry Wyatt and Yolanda McClary inspect a car used in the murder of Mattie Williams in TNT’s “Cold Justice.”

Collinston, Louisiana, is a place where everyone thought they knew each other — until Mattie Williams, the 67-year-old mother of 13, was murdered on Aug. 27. 2006. To say the town was rocked is an understatement. To hear the locals tell it in next Tuesday’s episode of TNT’s “Cold Justice,” Williams mothered everybody.

“When somebody like her gets murdered in a small town, it’s a huge thing,” says Yolanda McClary in the front seat of Kelly Siegler’s car as they drive to talk to the sheriff and then meet with Williams’ children.

McClary, a crime scene investigator from Las Vegas, and Siegler, a prosecutor, are unusual duo — two women with different backgrounds in criminal justice brought together to make a reality show about the settling of “cold” cases for the families of victims.

Their first stop: a meeting at the Morehouse Parish Sheriff’s office.

“Our goal is download your brain into ours,” says Siegler, a no-nonsense brunette with an impressive track record of convictions.

Still, it takes a lot of guts for two total strangers to drive into a close-knit community and get people to spill. Siegler looked through many cases before coming up with the roster that comprises the eight episodes of “Cold Justice.”

“We have to have the cops want us to help,” Siegler says. “They have to be wiling to share their information.”

“We don’t have jurisdiction,” McClary says.

They need a liaison to help them talk to Williams’ kids and find him in Sheriff Mike Tubbs.

The empathetic Siegler establishes immediate trust with one of Williams’ daughters, who wants to know what she and her siblings can expect to take away from the experience.

“We wouldn’t be here if we didn’t think we could [find the killer] baby,” she says.

The “Cold Justice” team didn’t have a lot of time — eight days — to make its case.

“If you’re working on a cold case in the big city, you can take your time going to a crime scene because word’s not going to get out that you’re going over there,” Siegler says. “In a small town you have a limited window where you can probe for information.”

In questioning the Williams children, it becomes clear that their brother, John, is a suspect. Siegler, McClary and the Morehouse sheriffs also conclude that Williams was not killed at home. After a few days of investigation, the team thinks they’ve found two suspects, but they get some bad news: the D.A. thinks there isn’t enough evidence to issue an arrest warrant.

Kelly and McClary did not know each other before “Cold Justice” and they had to find a way to bond on camera. “She’s country girl and I’m bling bling,” says McClary.

“Cold Justice” is tightly edited, with short scenes and just enough establishing shots of the town to stave off claustrophobia, but Siegler wants you to know, “It’s not just a TV show. We’re making cases prosecutable to win convictions.”

It’s a huge relief to the family that Siegler and McClary are able to make an arrest in the murder of Mattie Williams.

With their first season behind them, Siegler is looking for her next 10 cases.